Hi Sachin,
You can add an extra class for a block, then add specific custom css rule for it.
For example, when you edit that 'Gallery' page, hit the first block called 'Architectural Photography' >> click setting icon > Advanced tab > Extra class >> add a new class called 'architect'
Next, you define css rule with this new class:
.jub-block.gallery-4.architect .gallery-items .item img { min-height: 240px; }