You're going to have a very tough time separating those products unfortunately.  Have you tried using a combination of EtOAc and hexanes?

Unfortunately those structural differences are so small it's going to be impossible to find a staining agent that makes them different colors.  Sorry :\

is nasty , but the best tlc you get is with benzene and ethyl acetate or  MEK

normal phase silica is slightly acidic due to the empty silanols (Si-OH) groups. Amines are basic. Acidic Silica + Basic amine = bad tailing due to very strong adsorption/ionic interaction.
what you want is a modified phase. you can deactivate/modify the silica by pretreating the plate with ~0.1-1% conc. aq. ammonia in anhydrous methanol. After you have pretreated it (run the plate with the solvent mixture without any sample spots) dry the plate then spot and run with your solvent system of choice.
alternatively, you may run the plate already spotted with no pretreatment with a solvent system containing 0.1-4% aq. conc. ammonia.

In normal phase chromatography (silica, alumina) the compounds usually elute in reverse order of polarity. Least polar to most polar.  in general di-substituted amines are less polar then mono substituted which are less polar then primary. When other factors, such as acid/base interactions come into play, separation will be affected.
a good solvent system to separate DMT from NMT is found in RAPID SCREENING PROCEDURE FOR SOME “STREET DRUGS” BY THIN-LAYER CHROMATOGRAPHY, Brown and Griffin, J. Chromatogr., 64 (1972) 129-133. The system is Ethyl Acetate/n-propanol/28% aq. ammonia (40:30:3). DMT Rf = 0.48, NMT Rf=0.21.
I imagine it may work also for homologs.

another good general system is chloroform/methanol/aq. ammonia (85:15:0.1). dont have the rfs at hand, but it does separate amines.

Another way to avoid the acide/base interactions is to use a different stationary phase.
Alumina, either neutral or basic will give you good results (if you get neutral alumina, ask the supplier if they lean towards the acid range or basic range).
Chloroform/methanol in various combinations work well with alumina. Alumina, especially basic, is routinely used to purify mixtures of amines. The "basic" means it has been pretreated with base.

Another stationary phase good for such amines is Aminopropyl modified silica (silanols are labeled with aminopropyl group, bonded to give Si-CH2CH2CH2NH2). Its separation is usually operated at reverse phase conditions. It is more expensive then regular TLC plates, but if you have the funding it is probably the best solution.

Also, you should try ehrlich's reagent for colors and scan the plate to a pc (digital image may work). subtle differences in color can be extrapolated from such a pictogram. Various marquis combos may also give different color reactions (differences in time, color, color evolution). a bit Formaldehyde/Paraformaldehyde in sulfuric acid.

hope this helps, and plz post your results!

happy to help AB2. this actually turn out to be much easier then you think. If you look over my previous posts (search for it), you will see fully transparent DMT crystals i obtained from a quick short column post reaction. I loaded silica, pretreated it with ammonia/etoac/hexane, then ran the column with isocratic gradients. this was done according to tlc separation previously run on the actual reaction mixture. separation was super good and the single dmt spot was actually separated into 2 very close running spots - 1 is actual dmt, and is the major product, the other is something very similar in structure but non the less not DMT. I did not push it into the MS or NMR since i thought it would be a waste of time.
long story short, if you still have problems separating the isomers/homologs, i suggest carrying out a careful gradient separation. read up on AMD (automated multiple development). it can be done manually if you have time and offers unparalleled separations.

try immersion first. it is the best way to adsorb stuff onto the plate. if your plate disintegrates then try spraying/atomizing it, but i have no experience with this way.
otherwise, skip the pretreatment and just use an eluent mix that already contains the amine (ammonia or triethylamine) modifier like ive written above.
also, if you want to upgrade your separation power, spot a single mixture spot in one corner of the plate, run it normally, then flip it so that the compounds that separate will now run individually. it is called 2D TLC.

check your pm for synthetic details.

Thanks Wizard X, I'll see if I can track that reference down.