Hi Krish. The dark yellow colour urine is due to the presence of either infection/crystals/bilirubin or even due to less water intake. It can be ruled out only through urine analysis.
also he has been marking in most part of the house, it's been very hot here lately can this also be another factor?.. let me know if taking an appointment with you will work too, since there's no lab for dogs for urinalysis near me
Territory marking is most common in unneutered dogs or it is also due a reason that a pet is distressed due to one or the other reason. If the climate is hot, pets lose water content from body through sweating/panting, may be the amount of water your pet consuming is insufficient. Encourage him to take more fluids to compensate. Other than this, if you aren't finding any changes with respect to frequency or smell of urine, it's absolutely fine.