I used the 5/8 quillboar to double cast blood gems onto a corrupted myrmidon in the tavern, then doubled the health of minions in the tavern with the demon card. The turn after, I tried playing blood gems on the myrmidon on my board, but the gems only gave attack, not health. If relevant this was with the greater trinket that gives +4/+4 to blood gems. The tracker for blood gems the minion gained as buffs underneath the card was updating correctly.
Same happened to me after using the “double health in the tavern” demon buffer.
The tooltip actually shows the amount of health that the minion should have gained.
Not a visual bug.
imgur . com /a/L1TRwQC
I just had the opposite issue, no attack gained from blood gems. tried upgrading the gems to no avail, but bananas seemed to work fine.
It should be noted the blood gems were being properly tracked on the enchantments/buffs pop out when I hovered over the card