u/Clear-Dimension-1972

Help needed! I got these lithops last October from Home Depot. I then re-pot them in 70% perlite and 30% cactus soil. Only watered them lightly right after re-potting. I grow them indoors (zone 7b) on an east facing windowsill under a grow light (8 hours per day). They started to show signs of splitting in early February this year, but still haven't finished it after 3 months. Is this normal? Is there anything I could do? I touched them. They still feel firm.

The first picture was taken on Feb 1, then Mar 1, April 6, and May 4. I really appreciate any advice. Thank you so much!