FlytrapCare Carnivorous Plant Forums

Hey guys,
first of all, sorry for my english, i'm not a nativ english speaker..

I doing some TC aready some months. Mostley VFF and hardy Sundew. Now i'm starting with hardy Pinguicula but have some trouble, that i can't solve on my own.
My problem is, that the media always turns yellowish after a few days. In this enviorment the plants tend to turn brown and die if i dont replate them soon. I tried to change pH (5.0, 5.5, 5.8), tried to change sugar (20g, 25g, 30g), tried plainmedia and media with PGR, tried MS diluted to 1/4, 1/3, 1/2 (all with full micro nutrients AND full vitamins), tried solid media (Gelcaren) and liquid. But the problem stays...
If some guy has any idea, please give me some tips, that i can try.

I added a picture, that shows the problem. You can see cultures of P. vulgaris (yellowish) and right next to it on same media D. regia callus forming shoots (not yellowish).

Thanks in advice!
Bob