Hello,
It says ingame, by hovering over the ranked up turrets, that their damage is less than the non-ranked turret. This is likely due to research affecting only the base turret, not the ranked ones.
Is this only a visual issue, like the damage numbers are not updated, or do the displayed damage numbers actually reflects the ingame damage of the turret? If that is so, this is a pretty bad bug, as the ranked up turrets are way worse due to not being affected by damage research.

Note that Im using Krastorio 2 and Space Exploration

Unable to comment on if this is just a visual bug or not, but wanted to add that I am seeing the same issue, using K2 and SE as well.

It looks like unranked turrets as showing as part of Base game > Krastorio 2 > Combat Mechanics Overhaul > Hero Turrets, but when ranked they show as part of Hero Turrets (not even base game). Presumably this is cause the researched damage buffs to not be applied?

AephK, indeed, ive confirmed that it is not a visual bug, but the levelled up turrets do less damage. What I did was not exactly a fix, more of a patch work: I modded the game myself, and disable the extra damage turrets get from damage research, while increasing bullet damage per research. It was always pretty silly that turrets get an extra damage buff besides the ammo buff. Now, the only source of damage increase is the ammo, so all turrets are equally affected. Laser turrets work without issue, as the damage is directly related to their ammo, ie, laser damage. HOWEVER, flamethrower turrets do not get ANY upgrade effects from technology at all, as flamethrower tech directly increases turret damage only, and not their 'fuel'. Fortunately, even non-upgraded flamethrower turrets are OP as hell, but I have been unable to solve this issue in a quick and easy manner...

I noticed this as well but it's a little frustrating for modded fluid turrets that aren't as OP. I think hero turrets can also mess up animated fluid turrets where they don't shoot correctly when their attack speed increases.