Was the soil too hot for these Bubblegum Auto seedlings?

Probably- yes. Also keep in mind - ILGM are very hit and miss with genetic mutations, intersex (herm) issues, diseases and mosaic viruses common with their genetics as well. I used them for dozen or so strains and got fed up paying top dollar for shit that was a complete roll of the dice. The dark green color as well as inter-veinal chlorosis and necrosis would imply nute toxicities