It's a very...busy design, thats for sure.
And I've just noticed, you've stuck with 1.4. Like a boss ha!
Anyway.
Looks like you've got hidden engines buried in the core and booster sections. I don't know what kind of weights it lifts to LEO, but I'd bet not much more than 150t would be my guess and I'd hazard a guess from what I can see of these buried engines, your TWR is going to be high.
Coupled with the draggy nature of the way you've built the more...aesthetic elements of the rocket, this will punish you once drag acts on you.
My recommendations? As usual, this involves a good old engine swap.
Stage 2 I'd go with a pair, or trio of frontiers. I understand why you've used Titan cos of the mass of stage 2 plus everything above it needs that 3000kN of loving, but it's very inefficient.
Stage one and the boosters, I'd have a single Titan on each piece. That'll give you more than enough force to push an all up 900t rocket, which yours won't be even with payload.
What that does mean is booster burn out times are going to be after the core. They're not at the moment cos of the buried engines, but I'd suggest moving fuel mass from the boosters to the core so they drop away first.