I have seen crystals form in heavily reduced base solution where the solvent had become saturated and the basic solution/non polar was at a low temperature, some had been left as a thin layer following a pull. This has happened to me on a couple of occasions.
If you do have DMT precipated you could try warming it all in a water bath/sink when you do your next pulls.
If the amounts are significant you could try straining out the crystals. Strain crystals out, add plain water (if you are worried about losses due to your water’s pH you may wish to do this with sodium carbonate solution) and decant 2 or 3 times to give an initial clean, then re-x after.