Enemy buildings appear to become invulnerable on Easy mode

[Ayelis]

I've been trying to win a match, even on easy. Eventually after all my strategies seemed to fail, I focused on building rows upon rows of turret towers until I hit my build cap, and finally I could survive a match for more than 4 minutes. But now, after I've lost a few towers and built some heavy tanks to start an invasion, the enemy towers appear invulnerable, no matter how many heavy tanks I seem to throw at them. It's a nonstop stream of purple tanks, but my green tanks are picked off one by one, without even a single power plant falling, or even a single unprotected mining station. I can park them there all day and that mining station just eats up bullets with nothing to show. Perhaps it would be nice to see enemy building HP, to be sure they're actually taking damage. The enemy tanks are falling, but I haven't seemed to have put a dent in any of the buildings.