I didn't find anything to do with my dead units. Its just wait until the enemies kill my heart and try again....
So a bit unforgiving, not being able to respawn them and having to just wait. One mistake is usually game over.
Edit: I was able to heal back from death with the green liquid.
Finished the game. I think it was a bit too long for the game jam, they did say to make 5 minutes worth and this was much longer.
Apart from that, it was nice as a "protect the girl" type of game. The levels were pretty scripted as in there is an order to buy things.